Here's what I did with a few items from a 1920's bike racer.
Ad poster, racing license, photo, and a couple medals (Including a national championship) The mat doesn't really obscure anything, the flat items are held on with acid free photo corners, with a plastic overlay to keep the very thin poster from collapsing out of them.
The medals are stitched through the hanging loops onto the back piece of matboard, and one has an extra layer of matboard to give it enough room.
